1) Field of the Invention
The present invention relates generally to an air mattress. More particularly, the present invention relates to an improved air mattress that is more comfortable and has a less weight.
2) Description of Related Art
Air mattresses are used outdoors, at home, in the field of medical care, and so on, owing to their portability and easy storage. A conventional air mattress, as shown in FIG. 1, comprises a top sheet 101, a bottom sheet 102, annular connecting bands 103, and a side sheet 104. The top sheet 101, the bottom sheet 102, and the side sheet 104 are made of a flexible airtight material, for example, polyvinyl chloride (PVC), and these sheets are welded together to form an inflatable compartment. The annular connecting band 103 is disposed within the inflatable compartment, with its top and bottom welded to the top sheet 101 and the bottom sheet 102 respectively. When the air mattress is inflated, the annular connecting bands 103 restrain the top and bottom sheets 101 and 102 to such an extent that the inflatable compartment looks and feels like a bed. As shown in FIG. 2, the annular connecting band 103 is formed by connecting a flat connecting band end to end to form a ring containing a hole in its center. Therefore, the resulting connecting band is named an annular connecting band. As shown in FIG. 3, the annular connecting band 103 is welded to the top and bottom sheets 101 and 102 to form a welded joint 105. The welded joint 105 may be circular, elliptic, oval, hexagonal, octagonal, and so on. Alternatively, the annular connecting band may be substituted by an I-shaped connecting band. As shown in FIG. 4, I-shaped connecting bands 103′ are welded to the top and bottom sheets 101 and 102 to form linear welded joints 105′.
However, the known air mattress is made of three sheets of material, i.e. the top sheet, the bottom sheet, and the side sheet. Therefore, there are more welded joints between these three sheets, which requires more welding steps and takes more time. Further, when the inflated compartment is filled with air, under the action of the connecting bands, obvious projections and depressions are created on the surface of the air mattress, the depressions being positioned at the welded joints of the top sheet and the annular connecting bands, and the curved projections being positioned in the areas between the welded joints. As a result, the contact area between the surface of the air mattress and the human body is relatively small. With the I-shaped connecting bands, there also exist rectangular projections on the surface. This leads to poor flatness of the surface, and in use, the air mattress feels uncomfortable. In addition, if more connecting bands are provided, the surface will become more rigid and less flexible.
Furthermore, 90 percent of the present commercially available air mattresses are made of pure PVC, flocked PVC, PVC laminated polyester or nylon fabric, and so on. These air mattresses are provided with annular connecting bands, I-shaped connecting bands, or slightly modified variations thereof. The air mattress made of PVC mainly has the following disadvantages: (1) the air mattress of this type is heavy and thus has poor portability; (2) PVC material is easy to be pierced and worn out; (3) PVC material is brittle at a low temperature and thus is not cold resistant; (3) the air mattress is not environmentally friendly; (5) the air mattress has a poor flatness; (6) the material must have a sufficient thickness since high frequency moulding is used in the manufacture process to perform a large-area welding operation; (7) since the air mattress is provided with narrow welding joints and has small areas for receiving pulling forces, the welding joints are often disengaged under the action of pulling forces, thereby leaking gas from the air mattress; and (8) the manufacture process is complex, resulting in high manufacturing cost.